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See how your savings grow with the power of compound interest.
📈 Compound interest is "interest on interest" — the longer your time horizon, the more dramatic the growth. Starting early matters more than starting big.
Compound interestis interest earned on both your initial principal and the interest that accumulates over time. It's often called "interest on interest," and it's the most powerful force in long-term investing. Unlike simple interest, which only grows your original deposit, compounding makes your money grow exponentially — slowly at first, then dramatically faster as the years pass.
For a single deposit with no ongoing contributions:
A = P × (1 + r/n)nt
This calculator assumes monthly compounding and lets you add monthly contributions, which are calculated using the future value of an annuity formula.
Time matters more than the amount you invest. Consider two savers:
Despite investing only one-third as much money, Saver A still ends up meaningfully ahead — because their money had 30 extra years to compound.
Common reference rates for long-term investing:
Use 7% for stock-market-based long-term investing. Past performance doesn't guarantee future results, and returns vary year to year — but compounding works the same regardless.
A quick mental shortcut: divide 72 by your annual return rate to estimate how many years it takes to double your money. At 7%, money doubles in about 72 ÷ 7 ≈ 10.3 years. At 10%, it doubles in 7.2 years. This calculator gives you the exact number.
Disclaimer: This calculator is for informational and educational purposes only and does not constitute financial, investment, or legal advice. Calculated results are estimates based on the inputs you provide; actual figures may vary. Always consult a qualified professional before making financial decisions.
The Compound Interest Calculator lets you figure out compound interest calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
Common uses: people reach for this tool when they need to find a compound interest with monthly contributions, compound interest calculator with deposits, compounding frequency calculator, or future value with regular contributions.
Browser-based tools like this one have a few real advantages over installed software or manual methods:
The Compound Interest Calculator is based on the following formula:
A = P × (1 + r/n)^(n·t) + PMT × [((1 + r/n)^(n·t) − 1) / (r/n)]
Variables: A = Future value, total balance at the end ($) P = Initial principal ($) PMT = Contribution added each compounding period ($) r = Annual interest rate (as a decimal) n = Compounding periods per year t = Number of years
Compound interest (future value). P = initial principal, PMT = recurring periodic contribution, r = annual rate, n = compounding periods per year, t = years. A is the total balance at the end; the first term grows the principal and the second is the future value of the contributions.
Worked example: Step 1: P = $10,000, PMT = $200 per month, annual rate 6%, n = 12, t = 10 → r/n = 0.06 / 12 = 0.005 and n·t = 120 periods. Step 2: (1.005)^120 ≈ 1.8194. Step 3: principal term = 10,000 × 1.8194 = $18,194. Step 4: contributions term = 200 × (1.8194 − 1) / 0.005 = 200 × 163.88 = $32,776. Result: A = 18,194 + 32,776 ≈ $50,970 after 10 years.
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